Practice question

Translation unit conceptually frames messenger RNA segments decoded by ribosome, including 5' leader, open reading frame specifying amino acid chain from start codon AUG to stop codon, and 3' trailer. Open reading frame designation emphasizes continuous triplet codons without interruption that could encode protein when translated. Many transcripts contain upstream ORFs regulating main ORF via translational repression, while main ORF produces functional product. Bioinformatics prediction annotates longest ORF as candidate coding sequence. While replicon defines replication and cistron defines genetic complementation, ORF explicitly denotes nucleotide interval translatable.